Abstract: Data stored on a tape in a plurality of data recording sessions employs tape drive apparatus programmed to record the data in accordance with a format specifying a log of tape-usage information. The log is in the form of a data structure including a plurality of log sections in which tape usage information is recorded relating respectively to corresponding ones of the plurality of data recording sessions. The log sections together constitute a cumulative record of tape usage covering the corresponding plurality of recording sessions, each log section in respect of a recording session comprising an identifier of the tape drive apparatus used for that recording session and a count of the recording session.